Photometry of Long-Period Algol Binaries. IV. KU Cygni and Its Thick, Dusty Accretion Disk
Abstract
Five-color intermediate-band photometric observations of the totally eclipsing long-period binary KU Cygni were obtained from 1982 through 1987. Partial eclipses by the cool star of a large accretion disk around the hot gainer appear as light curve 'dips' bordering both sides of primary stellar eclipse. Secondary eclipse is abnormally broad and deep, and occurs when the accretion disk nearly completely occults the cool loser. These circumstances permit investigation of both the emitting and the light-blocking properties of this disk. Reconciling these properties requires that the pressure-supported disk be vertically thicker than expected from purely gravitational stratification, and that the outer part of the disk be slightly contaminated by dust particles, presumably accreted from the cool loser. Existence of 'high' and 'low' brightness states in this system suggests variable mass accretion by the gainer, at peak rates near 10 to the -6th solar masses/yr. The general implications of such a thick disk are briefly discussed.
- Publication:
-
The Astronomical Journal
- Pub Date:
- October 1988
- DOI:
- 10.1086/114895
- Bibcode:
- 1988AJ.....96.1439O
- Keywords:
-
- Accretion Disks;
- Astronomical Photometry;
- Cool Stars;
- Cygnus Constellation;
- Eclipsing Binary Stars;
- Light Curve;
- Hot Stars;
- Stellar Mass;
- Stellar Mass Accretion;
- Stellar Spectra;
- Astrophysics;
- STARS: INDIVIDUAL;
- STARS: ECLIPSING BINARIES